Tuesday, October 4, 2016

What’s happening on I-5 Fisher Creek?

By Andrea E. Petrich

I spent a lot of my August evenings watching the Olympics. It's amazing to watch those who are so skilled at their craft.

I often have that same sense of awe when I go to construction project sites. I definitely did this week when I visited a concrete pour in Skagit County. These guys made a messy, tough process look as smooth and easy as many Olympic athletes.

About the projects
The current Fisher Creek culvert under I-5 is just 8 feet wide.

Our contractor crews working on the I-5 Fisher Creek Fish Passage poured the deck of one of the new 110-foot bridges that will eventually take drivers over Fisher Creek.

Currently, a rusting metal 8-foot culvert funnels the creek underneath I-5. Replacing the narrow culvert with these wider two bridges will open up more than 17 miles of salmon and steelhead habitat and comply with a U.S. District Court ruling. But let's get back to what's happening now.

Building a bridge deck
Crews have been working on this project since May 2016, starting with the southbound bridge which is nearly ready for traffic. Recently, crews built a rebar structure as part of the deck before pouring more than 180 cubic yards of concrete into that structure.

It's a big job to get this concrete poured, smoothed, and protected before it starts to dry. It started with the concrete trucks. Every 12 minutes a new truck arrived to keep the material flowing. This operation used a huge pump boom (it's operated by remote control!) to move the concrete up into the air and out through a flexible tube that allowed crews to direct the concrete into the holes in the rebar.
Rebar is first constructed before we pour concrete into the structure.

A second person used a vibrating device to help flow the concrete into the many voids within the reinforcement. Other workers ensured there was a consistent amount of concrete before the Bidwell bridge paver moved in. The truss on this equipment is set up to work with the engineered grade of the road, in this case a slight crown in the middle to make sure water will flow off the bridge deck. That truss moved along the poured concrete with a traveling carriage that used an auger to initially break down the concrete mix and ensure the proper amount is in place before the stretch is rolled, smoothed and textured.
The entire operation was pretty impressive to watch, just like those Olympic performances. Crews moved quickly to get the concrete in and smooth before quickly covering it with wet burlap and white plastic.

This process is called wet curing, and it keeps the concrete from drying too quickly. While it takes longer to dry, the wet curing helps prevent cracking and extends the life of the bridge deck.

We cover wet concrete with burlap and plastic to keep it from drying too quickly and prevent cracking.

What's next
As crews wait for the deck to dry, they'll do prep work for the next steps – the approach to and off of the bridge deck and the barrier along the bridge deck. Both of these will require more rebar and more concrete. Crews will work to reopen the southbound lanes of I-5 to three lanes of traffic and move speeds there back up to 70 mph once all the pieces of the bridge are complete.

What travelers should expect
Completion of the southbound work doesn't mean this project is over, it means northbound work is coming. The current bypass lane for southbound drivers will be tweaked and modified. We are expecting that northbound I-5 in this stretch will start using the bypass lanes by the end of October. The interstate will become two lanes for drivers heading toward Mount Vernon and the speed will be reduced to 60 mph in this work zone. Both drivers and workers are pretty lucky with this project as we've been able to create a safe work zone for workers that includes a concrete barrier while drivers are experiencing a minimal slow-down without any complete lane closures.
Once crews detour northbound traffic, they'll work through the fall and winter on the northbound bridge. I'd expect work to be a little slower than southbound because they'll have varying weather conditions to deal with.

When crews finish the northbound bridge, they'll open three lanes of traffic back up and increase speeds while they complete work under the bridges to remove the existing culvert and expand the stream channel.  The entire project should wrap up a year from now when an improved Fisher Creek will be ready for fish to show off their Olympic style skills during the next spawning season.